The present invention relates to a device for confirming whether or not a cylinder lock is locked, and more particularly a device for confirming whether the cylinder lock is locked in which the ability to confirm whether cylinder lock is locked or unlocked is imparted to a key for the cylinder lock.
For instance, it is impossible to confirm whether a cylinder lock is kept locked or unlocked by merely looking at a corresponding key when one is outside so that there are many persons who feel anxious and return to confirm whether the cylinder lock is closed or not. In order to substantially solve this problem a locking mechanism in which a corresponding key is incorporated with a display device for displaying whether the cylinder lock is locked or not is disclosed in, for instance, Japanese Laid-Open Utility Model Application No. 47364/1986. However, such a locking mechanism can be applied only to an extremely small number of types of cylinder locks and it is impossible in practice to incorporate a single-pole, double-throw switch, which is one of the most important component parts, into a head of the corresponding key, so it will take a long time before such a locking mechanism is used in practice.
Furthermore, a key holding mechanism for controlling the cylinder locks at various shops, offices and so on in a single building by an off-line operation has been devised and used. According to such a mechanism, the last person who leaves a shop or the like inserts a key into a cylinder of this mechanism to lock a cylinder lock and hold (store) the key. The next morning when the first person arrives at the shop, he/she enters a coded number by using a magnetic card or a ten-key keyboard to release and then pull out the key and then uses this key to open the cylinder lock. This mechanism is highly evaluated as the first non-caretaker or self-service control mechanism. However, from the standpoint of safety supervision of the building, this mechanism has a very serious blind point in that it cannot confirm whether a person who has left his/her shop last has completely locked the cylinder lock of his/her shop.